FIELD OF THE INVENTION
The present invention relates principally but not exclusively to pacemaker stimulation leads.
Presently, only the head of the lead can receive electrical stimulation. This lead head introduced into the pulse generator is accessible only when the lead is disconnected and removed from the pulse generator.
The stimulation lead is practically always kept in place during replacement of a pulse generator. The manoeuver consists of disconnecting the lead from the pulse generator, removing it therefrom, reintroducing it into the new pulse generator and finally, reinserting the lead and pulse generator assembly under the skin.
This handling can require several tens of seconds.
In this case, as soon as the lead is disconnected, the patient is no longer being stimulated. This is no problem if the patient maintains a minimus of spontaneous cardiac rhythm, but some "dependent" patients have no spontaneous rhythm at all. They are then in cardiac arrest until the moment when the stimulation lead is connected to the new pulse generator.
In a dependant patient, then, the manoeuver is delicate, even dangerous.
One type of pacemaker lead with auxiliary stimulation pole is already known from French Patent 2,654,939, filed in the name of the Applicant, in which a break is provided in the strand sheathing reaching from the pacemaker to the electrode device for stimulation, making the lead conductor(s) accessible from the outside, the break possibly being insulated from the outside by a movable means such as a sleeve mounted sliding on said strand.
Despite the advantages in a practical sense of a movable covering sleeve, intended to mask the break in the insulated and protective sheathing of the internal conductor(s), can in time pose sealing problems and thus problems with the insulation of the conductor(s) vis-a-vis the medium surrounding the lead, which is a conductive medium and which could establish short-circuits between said conductor(s) and the pacemaker pulse generator.